1. Field Of The Invention
The present invention relates generally to tubing conveyed perforating systems, and particularly to such systems which are hydraulically actuated.
2. Description Of The Prior Art
One well known manner of completing an oil or gas well is through the use of a tubing conveyed completion system. A production tubing string has a packer located near a lower end thereof, and has a perforating gun suspended from the tubing string below the packer. The tubing string is lowered into place and the packer is set thus isolating the zone of the well below the packer. The perforating gun is then actuated to perforate the well casing adjacent the isolated zone and to allow formation fluid to immediately be produced up through the tubing string.
Many different techniques are known for actuating such tubing conveyed perforating guns. They can be mechanically actuated through use of a drop bar or slick line, and they can be hydraulically actuated by applying fluid pressure through a selected passageway.
It is also known to provide dual firing systems for a tubing conveyed perforating gun.
U.S. Pat. No. 4,836,109 to Wesson et al., and assigned to Halliburton Company, the assignee of the present invention, discloses a hydraulically actuated primary firing head utilizing a differential pressure actuating piston. The high pressure side of the actuating piston is communicated with well annulus pressure through a control line which extends below the packer. The low pressure side of the actuating piston is communicated with the isolated zone of the well. When the actuating piston is moved in response to an increase in well annulus pressure as communicated through the control line, a firing piston is released to initiate the firing of the perforating gun. A backup firing head is placed up on top of the primary firing head to provide an alternate means of firing the gun in the event the primary firing head fails to function or well conditions preclude the use of one of the systems after reaching total depth.
Other firing heads typical of those utilized by the assignee of the present invention include various mechanical and hydraulically actuated firing heads as shown on pages TCP-1001, TCP-1011, TCP-1013, TCP-1022, TCP-1014, TCP-1016, TCP-1020 and TCP-1018 of the Vann Systems Engineering Well Completion Product Catalog No. VS-0001 published by Vann Systems of Houston, TX, a division of Halliburton Company. Some of these structures such as the Time Delay Firing Head at pages TCP-1013, and the Pressure Actuated Firing Head at pages TCP-1022, contain a single actuating piston which also initiates the firing sequence, and is movable in response to an increase in tubing pressure.
U.S. Pat. No. 4,509,604 to Upchurch, and assigned to Schlumberger Technology Corporation discloses another pressure responsive tubing conveyed perforating system. It includes an actuating piston having its high pressure side communicated with the well annulus above the packer, and its low pressure side is communicated with the isolated zone of the well. Movement of the actuating piston releases a firing piston which initiates the firing sequence.
U.S. Pat. No. 4,523,643 to McGlothen, and assigned to Dresser Industries, Inc., discloses another hydraulically actuated tubing conveyed perforating system which operates in response to annulus pressure communicated from above the packer through a control line.